1. Field of the Invention
The present invention is directed to the preservation of wrapped and/or sealed foodstuffs. More specifically, the present invention is directed to the treatment of a perishable meat product preparatory to retail display.
2. Description of the Prior Art
Contemporary packaging of perishable products, and especially meat products, envisions maintaining the product in a controlled atmosphere from the time it is prepared at the packer until it is purchased by the consumer. Methods and apparatus to accomplish these objectives have been disclosed in U.S. Pat. Nos. 4,919,955, 5,352,467 and 5,481,852.
Several disadvantages however, exist with respect to the presentation of modified atmosphere packaged products to the consumer. One such disadvantage occurs when the product is sealed in a rigid tray with a flexible cover or film type lid. In instances where an enriched oxygen or carbon dioxide mixture is introduced into the package prior to presentation to the consumer, as is the case to promote a desirable "bloomed" color indicative of oxymyoglobin, the product must be sized so as to only partially fill the package resulting in a remaining void fraction or "headspace". This is because meat products readily respire upon the addition of soluble gases (e.g. oxygen or carbon dioxide). When these soluble gases are introduced into the package, they are absorbed into the meat tissue. This absorption continues for a protracted period which is known as the product shelf life. At the end of the shelf life, the product assumes a brownish color indicative of metmyoglobin.
Upon exposure to oxygen, the myoglobin pigment of muscle tissue is oxygenated. Carbon dioxide is dissolved in the water phase of the meat product. This absorption of these soluble gases results in the collapse or partial collapse of the hermetically sealed package lidding film. If the product is not proportionally undersized, the lidding film will be so tightly drawn downward due to the absorption of oxygen and carbon dioxide that the film touches the product. In the event of a meat product, the area of contact between the film and the product terminates respiration and as a consequence the product adopts an unpalatable brownish color indicative of metmyoglobin.
To avoid this phenomena, marketers of sealed products packaged in a modified atmosphere have adopted a process whereby a void fraction is built into the package in an amount proportional to its anticipated shelf life. In instances with an anticipated shelf life of 10 to 12 days, the void fraction is as large as the volume reserved for the product itself. As might be expected, this proposed solution is both unattractive and economically impractical since packaging and shipping costs are disproportionate to the volume of product.
Other disadvantages associated with packaged products include lack of moisture retention, or "purge". Purge occurs when the product is subjected to contact pressures such as those common in transport or those associated with a plastic film vacuum package. Purge also occurs when the product is subjected to temperatures above 40.degree. F. such as commonly occurs in the retailer display cabinet. Previously, no solutions have yet been proposed to address this phenomena.